1. Field of the Invention
The present invention relates to apparatus for vaporizing fuel droplets undergoing carburation. More specifically, the present invention relates to such an apparatus which utilizes heat from engine exhaust gases to vaporize the fuel.
2. Description of the Prior Art
Heretofore various methods and apparatus for fuel vaporization in internal combustion engines have been proposed, and several examples of such apparatus utilizing electric heating devices are disclosed in the following patents:
U.S. Pat. No. 3,556,065 issued Jan. 19, 1971 and U.S. Pat. No. 3,760,780, issued Sept. 25, 1973.
As disclosed in U.S. Pat. No. 3,556,065 it is found that optimum performance of an engine can be achieved by using electric heating devices to supply a certain amount of radiant heat into an air-fuel mixture, effective to cause the engine to develop maximum torque and acceleration while operating within normal ranges of load, speed and ambient temperature conditions and with the throttle valve of the engine fully opened, average torque and acceleration being reduced in proportion to a reduction in the amount of heat below the optimum amount and being also reduced in proportion to an increase in the amount of radiant heat above the optimum amount.
The electric heating devices disclosed in the prior patents are highly advantageous and in addition to producing a marked increase in torque and acceleration, such devices also produce, at the same time, an increase in efficiency. A great many tests have been conducted showing very substantial increases in gas mileage. Such devices do, however, require a substantial amount of electrical power which may, for example, be on the order of 55 watts for an engine having a displacement of 240 cubic inches, the required power being correspondingly lower or higher for smaller or larger engines. Also, considerable care must be exercised in constructing the electric heating elements of the devices to obtain reliable operation and long life.
In U.S. Pat. No. 3,985,112, issued on the application from which this application claims priority there is disclosed the use of a high temperature fluid flowing through an internal flow passage of a heater device to heat the heater device and to cause radiation of heat from the external surface thereof into fuel for vaporization thereof. The high temperature fluid is preferably engine exhaust gas which has very important advantages in that exhaust gas is conveniently available and also in that it provides a source of sufficient energy to produce a high enough temperature for radiation of an amount of heat into the fuel-air mixture approximately equal to that required for optimum performance. As further disclosed in U.S. Pat. No. 3,985,112 the supply of the high temperature fluid is controlled to maintain the exterior surface of the heating means at a certain temperature which may be changed in response to ambient temperature, the supply of the high temperature fluid being controllable through electrically operated valves, electrical signal generating temperature sensing means and electrical circuitry.
In the prior art, a number of apparatus using various forms of heating means in conjunction with carburetors and intake manifolds of internal combustion engines have been proposed. It is not known whether such apparatus have ever been actually used to obtain improved results and it is not readily apparent that any of the previously proposed apparatus would be operative to produce a significant improvement in performance of an engine during normal operating conditions. Although referring to temperature and heat control, the teachings of the prior art apparatus do not suggest or teach the amount of heat or the temperatures to be used or the control thereof to obtain optimum engine operation. Moreover, the previously proposed apparatus have been such that it would be difficult if not impossible to obtain temperatures and amounts of heat which provide optimum engine operation.
Included in the prior art are apparatus for heating the air or fuel prior to entry into a carburetor which may have advantages under certain conditions such as in cold weather starting or in warming up an engine, or when icy conditions exist, but which have severe disadvantages from the standpoint of engine performance in normal operating conditions. It is also quite common to apply exhaust heat to an intake manifold wall which is apparently advantageous during warming up of an engine but which is disadvantageous with respect to performance and normal operating conditions.
Also in the prior art literature there has been proposed a system which uses a vaporizer heated from exhaust manifold heat through a heat exchange liquid. It appears that such system would not be able to supply sufficient heat to the fuel at the proper temperature without undue heating of the air. The system also appears quite complicated with respect to construction, installation and operation and it appears that the flow of the air-fuel mixture might be unduly restricted.
Examples of previously proposed apparatus and methods of the types described above are disclosed in the following patents: